When the radio is on and I turn on the rear defroster, the radio has a lot static and is blank

Have diodes tested in the alternator .

there is a box on the heater were the radio wire goes to the back screen. when they fail they do this. now as for finding this box it could be on the pas side rear compartment or in the boot under the rear window. if you follow were the wire to the heated window go it will be on the end of the wires. you will need to change this or put an external aerial on. like I did my self on my own car.

Between the rear passenger window and the back window is a junction where rear defrost wiring and radio antenna connect. Rear defrost wiring becomes loose and burns this unit out. when looking for replacement at salvage yard everyone of them I found had burned up. Lots of La Sabres w/o working rear defrost. I made solid connections for defroster, and added an antennae, not much point in repeating a system that will fail again.

check the connections going in to the window leads and also with a test light ,check if their is power at the terminals that plug into the window leads. does your car still have factory warranty that the dealer can look into this.

Sounds like a bad connection to the defroster. Make sure that the power connections are a tight fit to the spade terminals

im having the same shift problem and radio static with rear defrost on

check for antenna ground if corroded relocalize the ground.

YES, THE RADIO ANTENNA IS PART OF THE DEFROST HEATER GRID.

The radio antenna is shared by the rear defroster, there is a part called the "Antenna Amplifier-Rear Window Defogger Coil", it is behind the left side rear pillar trim. It prevents the static from happening.

If the radio is aftermarket, they cross the circuitry of the antenna near the defroster, causing static in the antenna everytime you turn it on. Disassemble the radio and check for the wiring. Worst case scenario: they used the Positive wiring for the defogger switch and connected a wire to the radio's ACC cable.